We were discussing how to capture screen images easily the other day when I shared the Jackson Pollock link. I normally use hello (hello.com), which is free. Today though my dad (the freeware maniac) turned me on to FastStone Capture. http://www.faststone.org/FSCaptureDetail.htm
I've been using it for all of 5 minutes and I think I'm in love.
It'll capture the whole screen or just the window or just a freehand selection or a rectangle. It'll also let you magnify what's on your screen easily (click and hold and drag) - from 1.5 to 3X.
I love things like this.